Autonomous capsules, also referred to as “leadless capsules,” including without limitation autonomous intracardiac capsules (collectively hereinafter referred to as a “capsule”), are distinguished from wired electrodes and sensors that are placed at the distal end of a lead, and connected by a conductor traversing the length of the lead to a device connected at the opposite (proximal) end of the lead. Such capsules are, for example, described in US Patent Publication No. 2007/0088397 A1 and PCT Publication WO 2007/047681 A2 (Nanostim, Inc.) and US Patent Publication No. 2006/0136004 A1 (EBR Systems, Inc.).
These capsules are usually cylindrical structures having a long axis and a diameter. They are usually attached directly to the heart tissue by a projecting helical anchoring screw. The anchoring screw axially extends from the cylindrical body of the capsule and is designed to penetrate the heart tissue by screwing into the implant site.
Of course, to enable data exchange with a remote device, such capsules incorporate a transmitter/receiver for wireless communication with the remote device. A remote device in this context may be an active implantable medal device (e.g., a housing of stimulation pulse generator) or an external device such as a programmer or other device for monitoring a patient.
The capsule can also incorporate a sensor to locally measure the value of a parameter such as, for example, the oxygen level in the blood and/or the acceleration of the heart wall. These capsules can also be detection/stimulation capsules with means to collect depolarization potentials of the myocardium and/or deliver pacing pulses to the site where the capsule is implanted. Such a detection/stimulation capsule then includes an appropriate electrode, which can be, for example, an active portion of the anchoring screw.
In general, the capsule may be an epicardial capsule, attached to the outer wall of the heart, or an endocardial capsule, attached to the inner wall of a ventricular or an atrial cavity. However, It should be understood that the present invention is not limited to a particular type of capsule, and it applies equally to any type of capsule, regardless of its functional purpose.
In the case of an endocardial capsule, the difficulty of implantation is increased because the implantation path involves going through the peripheral venous system. With the assistance of fluoroscopy, the capsule may be directed to a selected implant site, a known method that is both precise and perfectly secure. Once the implant site is reached and the capsule is anchored in the wall, the operator may then operate the “release” of the capsule, and disconnect it from an associated implantation accessory.
US Patent Publication No. 2009/0204170 A1 (Cardiac Pacemakers, Inc.) describes a capsule for electrical stimulation and an accessory tool for its implantation, in which the capsule is guided by a catheter to the implant site within a directing tube pressed against the heart wall, and then progressively screwed into the heart wall by a driving stylet extending into the lumen of the catheter.
The general acceptance by persons of ordinary skill in the art of the use of endocardial capsules relies on an ability to provide a delivery system that is capable of securing the implantation of these capsules, according to the following:
An implantation procedure similar to current practice, allowing practitioners to make use of well-known and well-controlled lead manipulation gestures: e.g., subclavian puncture, insertion and manipulation of a catheter through preformed stylets during an approach to the selected implantation site, fixation with screws or tines, etc.;
Standard Environment in the Operating Room;
Limiting the risk of “carotage” of tissue due to an excessive tightening that may damage or, even worse, puncture the wall (especially in the case of implantation in a thin wall such as the atrial septum);
Possibility of postoperatively withdrawing and/or repositioning the capsule in case of problems, even after a release of the capsule from its delivery system;
Limiting the consequences of a capsule migration in case of displacement during the acute phase of an intervention; and
Certainty of a good anchoring of the capsule before removing the implantation accessory.